Duty
by The Infamous Fly
Summary: A Oneshot. Sans faces off with a genocidal human for the 100th time. But something is different. He can feel himself growing wearier. Will this be his final battle? Rated Mature for Gore, Death, Disturbing concepts, and adult language.


**Duty**

 **WARNING** _ **:**_ Contains Gore, Death, Adult Language, and Disturbing Concepts.

When Sans' text is like this = *blah blah blah.* he is speaking normally.

When it is like this _"Blah blah blah."_ he is using his serious voice.

* * *

Sans glared at the end of the hall, every bone in his body tensing in anticipation. He smiled in time to greet the approaching human. Frisk's clothes were coated in blood and dirt, their face not much better. Dirty bandages, most likely stolen, peeled off of their arms as they heaved for breath. The dagger in their left hand scratched against the marble floor as they shuffled forward, hunched over like the beast that they were.

Sans looked them up and down, *you're not lookin' too good kid.*

The murderous child glared at up him and began to straighten.

Sans repeated his warning as Frisk stumbled closer, knowing full well that they would not listen. *i made a promise to someone very important to me to protect you. yadayadayada, you know the drill by now, i don't want to break that promise.*

His eyes disappeared and a glowing eyeball rolled into place as his voice shifted in tone and octave, _"So turn around, and go back from whatever pit in hell you climbed out of."_

Frisk seethed, their hands shaking as they looked him up and down.

Sans raised an eyebrow, _"Well someone has died an awful lot…"_

Then the child did the one thing which he did not expect them to. They spoke.

"99."

Sans tried not to look too surprised at the words. He was stunned, not only that none of the other Sans had been lazy enough to give in, but also that this little psycho was determined to keep on going. found his grin widen. It was simultaneously depressing and impressive.

He found his grin widen. _"Was it worth it?"_

Frisk didn't answer, instead shuddering and spitting out blood. Sans noticed their bruised lip and examined himself. He was untouched, as always, but felt rather exhausted. As though he had just fought a hundred battles. The timeline was bleeding from excessive use. It was clear that this time, the fight would be different.

For this he smiled a little brighter, finding the situation less disturbing and more humorous than usual.

He commented with an outstretched hand. *so…you wanna spare me?*

Frisk glared daggers as the skeleton laughed at their expense, and then raised their weapon.

They stepped over the invisible line, as they had done apparently ninety times previous, and spoke with a smug voice. "I'm going to smash you to bits just like I did with your retarded brother."

Sans stopped laughing. The blue flame returned to his eye, and he cracked his neck, then his hands. His boots shuddered as power coursed through him, winding around each bone and preparing to be let free. He felt the power which he had worked so hard to achieve, begin to burn inside him. The energy was alive as the two of them, and it was relishing this opportunity more than him.

 _"If that's the way you want it, kid…"_

He had been here so long, fighting this same lunatic. Here, all alone, awaiting his own end. He was the singular wall between this creature and the destruction of the world. Everyone relied upon him. So he shrugged off the guilt, the loneliness, and the longing for their eternal duel to cease. Instead, he thought of all the reasons why he was doing this. He recalled all the chances which this kid had been given to end the path which they had gone down. Instead, Frisk had ruined his life. Even if he won this fight, he would be alone. His friends, family, and neighbors were all gone. This little bitch had made his life into hell, and he figured it was jus about time to return the favor. A dull hatred within turned into savage rage. As his anger built, blue fire began to spin around him were as he summoned two Gaster Blasters to either side of him. He grinned like a lunatic, as rage manifested itself as the bloodlust.

 _"THEN THAT'S HOW YOU'LL GET IT!"_

Bones smashed up through the ground, charging towards the child and then flying through the air like boomerangs. He laughed as Frisk jumped back and forth, avoiding every attack with demonic grace. They glared at him and sprinted forward. Sans dodged the first swing of the blade and then teleported behind the child after the second. The Gaster Blasters flew towards his foe, opening their mouths and sending a wave of caustic energy at the murderer.

The ground where Frisk had been scorched as Sans sent a wave of bones flooding towards his enemy. They tore through the marble, jabbing their blunt ends at the child. They jumped towards the back of the hall, and bones stabbed out. Frisk managed to avoid them but received a blast of energy from the attacking dragon skull. They felt to the floor, radiating with pain. Sans smirked, and caused a wall of bones to surrounding himself as he stepped closer.

*you a masochist or somethin?* He asked as he juggled a bone between both hands.

Frisk jumped to their feet with a growl and slashed at his chest. The bones caught the blow but Frisk attacked again. Sans leaped back, bounding off of a nearby pillar, and landing a close to the door to the palace. He raised a hand, and the dragon skulls tore after Frisk. They dodged each and every blast of power, smirking as they watched Sans begin to grow weary. Fearing that this would be the timeline in which he failed, the skeleton smashed all of the dragon skulls into the nearest pillar. It wobbled with each fiery explosion and then crashed towards Frisk. Dust filled the air as it struck the ground, and Sans waited impatiently for the result of his action.

Giggling filled the hall, as the cloud dissipated, revealing the unharmed Frisk. "Flowey told me you were worthless. Called you Papyrus' trashy brother."

Sans wiped sweat from his brow, unsure how much longer he could keep this up. *oh? did he insult my mother too?*

Frisk ignored the comment, continuing forward. "But he had it all wrong. Papyrus was the trashy one."

Sans snarled, his eye turning golden as his fingertips buzzed with sparks. Frisk continued regardless.

"You're more powerful than that stupid little flower could ever be…You…you are probably the most powerful monster in this entire world…"

*are you gonna fight me or ask me on a date?*

Again Frisk ignored his ill-timed humor, "You have so much potential. You could have killed those children who passed through Snowdin. You could have entered the human world…killed more of them, and become a god."

Sans glared at them, before speaking. _"Believe it or not kid…there's more to life than scrabbling to try and be more powerful than the next guy. I know."_

Frisk snorted, "You're just saying that because you are lazy and content. My parents warned me about people like you, fools that they were, they knew what was wrong with the world. And it was a lack of ambition."

Sans looked them up and down, *you sure that they were your parent's? cause according to my research, you got spat up by yak instead of being born…*

Frisk roared, charging at him with a flashing blade. Sans moved slightly to the side and reached out. Frisk had to change direction to stop from slamming into the wall, and Sans shoved them in the chest as soon as they were off balance. They struck the floor and groaned in pain. Their knife clattered beside them, and Sans smashed it in two with one well-placed stomp.

*The thing that people like you will never realize…*

Frisk took one look at heir broken weapon and tried to scramble away. Sans reached down and gripped their sweater before they could, noticing the fear which crossed their face as he pulled them to his level. _Good. You should be scared._ He bared his teeth and lifted Frisk just above him. The golden light of the outside buildings filtered through the stain glass windows and spilled upon his foe.

He ignored their protests and struggling, addressing them in dark and heavy voice. _"…is just how very SMALL you are!"_

Frisk's eyes widened, but they weren't given any further time to react. The skeleton's eyes burned with azure fire as he opened his mouth. The blue coloration of the fire was indicative that it was hotter than any other fire heh ad created over the past 99 timelines. Flame streamed out, and after what seemed like an eternity of screaming, the child ceased wriggling about and went limp. Sans dropped the corpse, feeling tears begin to well in his eye sockets.

Papyrus had always believed that there was good in everyone. A chance for redemption. That bad people were just good people who did bad things. Well, what did that make him? A bad person who did good things? Either way, his brother would have been disappointed in him. He was always telling him about his duty, about how lazy he was. But when Sans finally worked up the nerve to do what needed to be done, his little brother was dust. He got the feeling that Papyrus wouldn't be very proud of him either.

Having blamed himself into more tears, he spoke with a tight throat. *i'm so sorry bro…I never meant to turn into this…*

He turned away from the disfigured corpse, trying to console himself with the knowledge that he had just saved a city full of his kind. That he had saved all the humans as well. There would be no 101st fight, this was the last one. He had promised himself that he wouldn't let any more families be destroyed because of this little monster. He knew what would happen, he had done the _right_ thing to do, even if it had not been the _good_ thing.

But all he could think of was the screams which filled his mind as the little brother-killer had died. He didn't think he would be seeing any more of Frisk. Nor their ally, that stupid flower. He had just traumatized his foe. Burned off their face, showed them greater pain than they're abusive parents would have been able to, had they been given a million years. He had kept Frisk _alive_ while the blue flame burned away at their face, so that they might experience maximum pain, and never again challenge them.

He turned his eye upon the exposed skull of his enemy and tried to laugh through the pain which he felt inside. _"Who's the trashy-skeleton now?"_

The joke tasted bitter on his lips, and when he chuckled, it sounded more like a sob than anything else. For a moment it was him and the body all alone. Then he felt time begin to walk backward. He smiled with the knowledge that SOME of this would be lost to his memory. But those screams of agony, he got the feeling that it would stay with him forever. Across all timelines, and echoing beyond any dimensional barrier.

There was no escape from this responsibility.

* * *

 _ **Tell me what you think in a review? Too dark? I hope I caught the moral complexity and I didn't make Sans seem out of character. He's my favorite and I would hate to do him wrong. Leave a review and thanks for reading!**_


End file.
